The integrity of seals is often a critical element in the operation of various items. Nowhere is this truer than in doors, especially watertight doors, on ships. Watertight doors and hatches are critical to controlling flooding on ships and submarines. These doors often handle large amounts of traffic, cycling the doors open and shut several thousand times a week, causing the seal integrity to fade. Such doors often require extensive adjustments and maintenance in order to maintain a fluid tight closure. The twisting and flexing that occurs on ships cause doors to warp or bend resulting in loss of seal integrity. Other than periodic spot checks, there is currently no way to check the seal integrity on a continuous basis.
The current way to check seal integrity of watertight doors is to perform a chalk test. The chalk test is a simple means of determining if the gasket is in continuous contact with the knife-edge of the doorframe when the door is closed. Chalk is rubbed on the knife-edge of the doorframe and the door is shut and dogged tight. The door is then opened and the chalk line on the seal should be continuous if the door is adjusted properly. A non-continuous chalk line on the gasket indicates that the dogs are not pressing the gasket against the knife-edge properly. However, the chalk test does not guarantee that the door is watertight, as it does not measure seal compression.
Chalk tests are preformed on a periodic basis as it is a labor-intensive test. Doors and doorframes, especially the knife-edges, are subject to wear and tear with repeated use. Additionally, the frames and surrounding structures are often subject to stresses that may warp or bend the frames or surrounding structure. This may mean that even though the chalk test was successful, subsequent damage to the door or frame might occur that causes a bad fit that will not be discovered until the next chalk test.
Another method used to check seal integrity uses acoustic transducers. In this test, transducers are placed on one side of a closed door to produce acoustic energy and the quality of the seal is surmised based on the amount of acoustic energy received. However, such a method is labor intensive and does not-provide continuous feedback.
What is needed is an apparatus that can quickly and continuously determine if the seal is engaged adequately on a closed door.